An off-duty Montgomery County police officer shot and killed a Rottweiler yesterday after it bit the officer's wrist as he tried to confine it.

The officer had successfully leashed a second Rottweiler after receiving reports that two dogs were roaming an elementary school playground in the Aspen Hill area southeast of Rockville.

The shooting incident touched off fresh concerns in a community already shaken by the Sept. 15 attack by three Rottweilers on Arlynn Joffe and her 3-year-old son in Rockville.

As Joffe held her son in her arms, the dogs repeatedly bit her on the legs and thighs. She was hospitalized and required 150 stitches for her wounds. The dogs were allowed to live but were ordered removed from Rockville.

Police and animal control workers have not identified the owner of the dogs in yesterday's incident. The surviving dog was taken to the county animal shelter in Rockville, where it will be held at least 72 hours pending a claim by the owner.

According to police and interviews with school officials and students, the two male dogs appeared between 12:30 and 1 p.m. on the playground of St. Jude Catholic School while about 150 children were outside for recess.

As the dogs walked around the yard, then sat on an embankment, a few students began screaming. Others, however, petted the dogs, who did not appear menacing, teacher Paul Graham said.

A playground monitor called the animal control department, then alerted the off-duty police officer who was in the neighborhood.

Officer William Decourcy followed the dogs as they left the playground and cornered them on Pemrose Street, where he used a piece of rope to tie one of the dogs to a porch beam in the back yard of Maria Montano.

As he went for the second dog, it clamped down on Decourcy's wrist with its mouth and the officer drew his gun and shot it, said police spokesman Sgt. Harry Geehreng. Decourcy did not require medical treatment.

Montano, who was watching television at the time with the windows open, said she heard no barking but did hear a gun shot.

"We heard the shots," Montano said in Spanish. "When we went to the window, we saw it was a dog that had been killed."

She said that she and a family member were ordered back into the house by police and told not to leave.

The family was not exactly sure why there were so many police officers -- at least three cruisers came to the scene -- and, ultimately, television camera crews in her front yard.

"We didn't know why we couldn't go out. We don't speak any English. All I could understand is that we couldn't leave," she said.

Montano said she had not seen the dogs before and has no idea who the owner is.